Hydraulic hose

ABSTRACT

An apparatus and method for producing an hydraulic hose having ends of different internal diameters. An uncured hose is produced by conventional extrusion. The uncured hose is placed upon a mandrel having a reduced diameter end. That end of the uncured hose proximate the reduced diameter of the mandrel is covered by a heat responsive shrink tube. The shrink tube is heated to mold the end of the hose about the mandrel. Thereafter, the hose is vulcanized.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional patent application of its parent patentapplication, Ser. No. 584,849 now U.S. Pat. No. 5,686,041 filed Jan. 11,1996.

BACKGROUND OF THE INVENTION

This invention relates to the production of elastomeric pressurizedfluid conveying system hoses and more particularly to a method ofproducing a pressurized fluid conveying system hose having ends ofdifferent diameter. Such hoses are commonly used in automotive vehiclesfor carrying hydraulic fluid between a pump, a reservoir and anhydraulic device such as a power steering unit. These hoses, commonlycalled hydraulic hoses, are customarily of uniform internal diameter andare clamped or coupled at each end to a nipple having an externaldiameter substantially equal to the internal diameter of the hose. Thiscreates a design constraint for the equipment being serviced by thehose. Oftentimes it is desirable to present the hose ends to nipples ofdifferent external diameter. This requires an hydraulic hose having endsof different internal diameter. Heretofore there has been no economicalway of producing a hose having a reduced diameter on at least one end.

It is known in the prior art to build a hose upon a mandrel in such away as to produce an end of slightly reduced diameter, as shown, forexample, in Greacen U.S. Pat. No. 165,324. However, the Greacen methodproceeds by a complicated series of steps involving placement andpositioning on the mandrel of a rubber core, a helically coiled,tempered and untempered steel wire and a suitable covering material. Itis also known to place a hose upon a mandrel for curing and to wrap thehose with shrink film to compress it against the mandrel, as taught byBorden U.S. Pat. No. 3,752,719. Other prior art, such as Badberg et. al.U.S. Pat. No. 4,171,118, reshapes a cylindrical hose into a hose ofcomplex configuration by vulcanization upon a specially shaped mandrelhaving at least one end enlarged.

SUMMARY OF THE INVENTION

This invention provides a method of producing an hydraulic hose adaptedto carry hydraulic fluid between nipples of different diameter. Themethod involves producing of an uncured hose of uniform diameter andplacing the uncured hose over a mandrel of non-uniform crossection. Themandrel has a diameter at one end which is substantially the same as theinternal diameter of the uncured hose and a diameter at the other endwhich is substantially less. The uncured hose is placed on the mandrelin such a manner as to span the length of the mandrel between thecrossections of different diameter. After the hose has been seated onthe mandrel, the end of the hose is fitted with a heat responsive shrinktube. The shrink tube is heated to mold the uncured hose about themandrel. Thereafter, the hose is vulcanized, preferably with the tubestill in place. Following vulcanization, the shrink tube may be strippedfrom the hose. Preferably the mandrel is coated with a suitablelubricant for reception of the uncured hose. Also, the end of theuncured hose preferably is covered by a lubricant so as to facilitateremoval of the shrink tube following vulcanization.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a flow chart illustrating the method of this invention.

FIG. 2 is a schematic illustration of an uncured hose being placed upona mandrel.

FIG. 3 is an illustration of an uncured hose in position upon a mandrel.

FIG. 4 is a schematic illustration of a shrink tube in place about anend of an uncured hydraulic hose.

FIG. 5 illustrates an uncured hose having a shrink tube reduced tosnugly fit the O.D. of the uncured hose.

FIG. 6 illustrates a cured hose following molding by vulcanization withthe shrink tube.

FIG. 7 illustrates an hydraulic hose produced in accordance with thisinvention.

FIG. 8 illustrates a mandrel for use in this invention having multiplesize reductions.

FIG. 9 illustrates an uncured hose mounted upon the mandrel of FIG. 8.

FIG. 10 illustrates a cured hose following simultaneous molding byvulcanization on the mandrel of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Production of an hydraulic hose in accordance with this inventionproceeds as illustrated by the flow chart of FIG. 1 and commences atblock 10 with formation of an uncured elastomeric hose of substantiallyuniform internal diameter. The hose may be of rubber or synthetic rubberand may be produced by a conventional extrusion process. Suitablemethods for extruding such an uncured hose are taught in Miller et al,U.S. Pat. No. 3,824,141 and in Derderian et al U.S. Pat. No. 3,972,757.A typically resulting uncured hose may have an internal diameter ofabout 0.75 inches and an external diameter of about 1.09 inches. Such anuncured hydraulic hose may appear as indicated by reference numeral 30of FIGS. 2-6.

After the uncured hose 30 has been produced, it is placed upon a mandrel32, as illustrated in FIG. 2. Mandrel 32 may have an enlarged end 32a, atransition section 32b, and a reduced end 32c. The end 32a should have adiameter substantially equal to the internal diameter of the uncuredhose 30, while end 32c may have a substantially smaller diameter. In atypical application where the uncured hose has an internal diameter of0.75 inches, mandrel 32 may have a diameter of 0.75 inches at the end32a and a diameter of about 0.61 inches at end 32c.

As illustrated in FIG. 2, uncured hose 30 is placed over the smaller end32c of mandrel 32 and then worked up over transition section 32b ontothe enlarged end 32a. This placement may be facilitated by applying asuitable lubricant to end 32a of mandrel 32. A wide variety of suitablelubricants are commercially available. One lubricant which has beentested and found to be satisfactory is sold commercially under thetrademark "UCON." This lubricating step is indicated in FIG. 1 at block12.

FIG. 3 indicates the position of the mandrel 32 following fill insertioninto uncured hose 30. It will be noted that uncured hose spans thelength of the mandrel between ends 32a, 32c. Placement of uncured hose30 upon mandrel 32 is indicated by block 14 of FIG. 1.

After the uncured hose has been mounted upon the mandrel, the methodproceeds to the step of block 16 wherein a lubricant is placed upon theend of uncured hose 30 proximate reduced end 32c of mandrel 32. Thislubricant facilitates removal of a shrink tube as hereinafter described.Again, UCON lubricating liquid or a similar product may be used.

As indicated by block 18 of FIG. 1, the next step in the processinvolves the mounting of a shrink tube on uncured hose 30. Such a shrinktube is indicated by reference numeral 34 of FIG. 4. The internaldiameter of shrink tube 34 should be slightly greater than the externaldiameter of uncured hose 30, as illustrated in FIG. 4 by the referencenumeral 35. In a typical case where the exterior diameter of uncuredhose 30 is about 1.09 inches, shrink tube 34 may have an internaldiameter of about 1.31 inches. A suitable shrink tube for the purpose issold commercially by Raychem under the trademark "RNF-3000." This tubingis made from a proprietary radiation cross-linked polyolefin materialand has a shrink ratio of 3:1 when heated to 120° C. A satisfactoryshrink tube of the above internal diameter has a wall thickness of about1.15 millimeters.

Heat shrinking of the tube 34 is indicated by block 20 of FIG. 1. Heatapplication for this purpose may be accomplished by blowing hot air overshrink tube 34. Heating and shrinking proceeds until shrink tube 34 issnugly fitted against uncured hose 30, as illustrated in FIG. 5. After asnug fit has been achieved, uncured hose 30 is vulcanized with shrinktube 34 in place, as indicated by block 22 of FIG. 1. This step curesthe hose while concomitantly causing further shrinking of shrink tube34. Vulcanizing continues until hose 30 has been fully molded aboutreduced end 32C of mandrel 32 and cured. This is illustrated in FIG. 6.

Vulcanizing (or curing) is carried out in the conventional manner in avulcanizing oven at a temperature of about 320° F. for about 20 minutes.Thereafter shrink tube 34 may be stripped from hose 30, and hose 30 maybe removed from mandrel 32, as indicated by blocks 24 and 26 of FIG. 1.FIG. 7 illustrates the finished product.

It will be appreciated that further processing steps may be performedupon the cured hose 30, either prior to or following removal frommandrel 32. Also, hose 30 may be removed from mandrel 32 with shrinktube 34 in place. These alternatives are indicated by dotted lines onFIG. 1.

The above method has been performed repeatedly with good results inreducing a rubber hose from an internal diameter of 0.75 inches to aninternal diameter of 0.61 inches. Good results have also been obtainedin achieving other diameter reductions. For a reduction from 0.75 inchesto 0.49 inches (internal diameters) two shrink tubes are preferred. Thefirst step involves the application of heat to shrink tube 34 until theshrink tube 34 is snugly fitted against the uncured hose 30 as describedabove. Then a second shrink tube (not illustrated) is placed over thefirst shrink tube and heated until a snug fit has been achieved. Avulcanizing step then produces the final desired shrink.

Even greater hose end reductions are possible through use of multipletubes. Such a multiple reduction may be carried out with the aid of amandrel 132, as illustrated in FIG. 8. Mandrel 132 may have a fulldiameter section 134, joined to a plurality of reduced diameter sections136a, 136b and 136c by a plurality of transition sections 138a, 138b and138c. In use an uncured hose 130 is placed over mandrel 132 and fittedwith a first shrink tube 140 which spans the distance from the smallestend 136c beyond the first reduced diameter section 138a, as illustratedin FIG. 9. Then hose 130 and shrink tube 140 are heated until shrinktube 140 is snugly fitted against the uncured hose 130. At this point asecond shrink tube 150 is applied spanning the length from the smallestend 136c beyond the second reduced diameter section 138b, and a secondheating step is performed shrinking the second tube snugly against thefirst tube. Following this step a third shrink tube 160 is applied,spanning the length from the end 136c beyond the final transition 138c.A third heating step shrinks the third tube snugly against the secondtube. Thereafter, the vulcanizing step reduces the uncured hoseconforming same to the mandrel. This arrangement has successfullyreduced a hose end from an initial inside diameter of 0.75 inch to afinal inside diameter of 0.25 inch.

Still other applications of the method of this invention are possible.For example, the mandrel may be provided with a section of elliptical,or slightly flattened crossection. The circumference of this portion ofthe mandrel may be reduced in the order of about 10 percent from theinside circumference of the uncured hose, thereby facilitating removalof the hose from the mandrel while still warm from vulcanization.

While the method herein described constitutes a preferred embodiment ofthis invention, it is to be understood that the invention is not limitedto this precise method, and that changes may be made without departingfrom the scope of the invention, which is defined in the appendedclaims.

What is claimed is:
 1. An hydraulic hose produced by the method of:(a)extruding an elastomeric hose to produce an uncured hydraulic hosehaving a substantially uniform inside diameter; (b) pushing said uncuredhydraulic hose over a mandrel, said mandrel having a substantiallycylindrical first end of a first predetermined diameter substantiallyequal to said inside diameter, a substantially cylindrical second end ofa second predetermined diameter substantially less than said firstpredetermined diameter and a transition section therebetween, saidpushing being continued until said uncured hydraulic hose spans thelength of said mandrel between said first end of said mandrel and saidsecond end of said mandrel; (c) placing a heat responsive shrink tubearound said first end of said uncured hydraulic hose, said shrink tubecovering said first end of said uncured hydraulic hose and extendingtherefrom to a portion of said hose supported by said transition sectionof said mandrel; (d) applying heat to said shrink tube in sufficientamount to cause said shrink tube to shrink into engagement with saiduncured hydraulic hose; and (e) applying heat to said shrink tube and tosaid uncured hydraulic hose, said heat being sufficient to mold saidfirst end of said uncured hydraulic hose about said second end of saidmandrel and cure said uncured hydraulic hose.
 2. An hydraulic hoseproduced by the method of claim 1 wherein heat is applied to said shrinktube and to said uncured hydraulic hose at a first level for asufficient period to time to mold said first end of said uncuredhydraulic hose about said second end of said mandrel, said heatthereafter being raised to a higher level for curing said uncuredhydraulic hose.
 3. An hydraulic hose produced according to the method ofclaim 2 where said tube is maintained in contact with said uncuredhydraulic hose during said curing.
 4. An hydraulic hose produced by themethod of claim 3, further comprising the steps of:(a) lubricating saidmandrel prior to said pushing step; and (b) lubricating said uncuredhydraulic hose exteriorly about said end prior to said placing step. 5.An hydraulic hose produced by the method of claim 4, further comprisingthe step of removing said tube from said hydraulic hose following saidapplying step.
 6. An hydraulic hose produced by the method of claim 5wherein said first level is approximately 250° F., and said higher levelis approximately 331° F. and is maintained for approximately 21 minutes.7. An hydraulic hose produced by the method of claim 6 wherein saidfirst predetermined diameter of said mandrel is approximately 0.75inches and said second predetermined diameter of said mandrel isapproximately 0.61 inches.